My Mazda B4000/Ford Ranger keeps eating thermostats. The thermostat sticks after replacement after a week or two the engine overheats and pushes coolant out to the recovery tank. The temp gauge pegs for about 10 seconds then goes to normal. Pull the thermostat and it is stuck shut. Someone suggested that it may not be a thermostat but maybe a head gasket and when a pocket develops it damages the t'stat. I've had the vehicle in the shop to test the cooling system and it holds pressure at operating temp and cold. They also did a leak down test on all 6 cylinders with nothing conclusive. It never loses coolant other than what is pushed out to the tank. Whenever I refill the system I run the engine without the cap and there is no 'air' or bubbles coming out of the radiator. Even with a pressure tester the pressure is about 18lbs when hot. Radiator cap has been replace twice. This is very puzzling and becoming annoying. Engine is a Ford 4.0L V6. I had the engine flushed about 6 months ago and had 1 incident afterwards and change the t'stat and all was fine during the winter. then all of a sudden this has be recurring. I've gone through 4 t'stats in the last 5 or so weeks. I'm wondering if the coolant is contaminated and deposits are jamming the t'stat. Every t'stat I remove has this white substance on it. Anyone have any ideas?
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4/30/11 at 1:36pm